RPOJECT SUMMARY/ABSTRACT Adoptive cell transfer (ACT) of in vitro activated T cells into the recipient animals has been widely used to study the dynamics of T cell migration and differentiation and the process of effector functions in several disease models including acute/chronic inflammation, autoimmune disease, and graft rejection. Clinically, ACT has emerged as a promising therapeutic approach with complete and durable responses in several infectious and malignant diseases. For example, ACT utilizing genetically engineered cytotoxic T lymphocytes (CTLs) (e.g., chimeric antigen receptor (CAR)-T cells) has proven effective in treating many types of cancer. However, early studies on the fate of activated cloned CD8+ T cells after intravenous transfer into normal recipient mice indicated that these differentiated effector T cells are primarily retained in the non-inflamed tissues for a prolonged period before they become available in the blood for the subsequent migration into inflamed tissues. We demonstrated that the migration and retention of adoptively transferred activated effector CD8 T cells in the lung microcirculation is mediated by integrin LFA-1 (lymphocyte function-associated antigen-1 or ?L?2; CD11a/CD18), while it is insensitive to pertussis toxin (PTx). Spontaneous/chemokine-independent migration of in vitro activated CD8 T cells is closely associated with the dramatic down-regulation of an LFA-1-associated cytoskeletal protein, ?II-spectrin, and distinct endosomal redistribution patterns of LFA-1 in activated CD8 T cells. We hypothesize that CD8 T cells acquire key cell intrinsic cues during strong in vitro activation, which allows chemokine-independent LFA-1 activation and T cell migration into non-inflamed tissue sites upon intravenous transfer. We will, (1) determine the molecular mechanisms for chemokine- independent migration of activated CD8 T cells and (2) test whether we can generate T cells with an improved tissue-specific homing property. The molecular and cellular characterization of chemokine-independent, spontaneous migration of highly activated CD8 T cells will open up new therapeutic possibilities for inflammatory diseases. The effectiveness of clinical approaches using ACT may be specifically enhanced by our discovery of important mediators that can improve (chemokine-dependent) tissue-specific migration of adoptively transferred T cells while minimizing the (chemokine-independent) sequestration at non-inflamed tissues.